Non-aqueous electrolyte secondary battery and process for the preparation thereof

Abstract

In accordance with the non-aqueous electrolyte secondary battery of the invention and the process for the preparation thereof, charging is carried out with a combination of a positive electrode provided with excess lithium and a negative electrode in order to cause lithium to be deposited on the negative electrode. Accordingly, no oxidized surface film is interposed between lithium and the current collector of negative electrode or the negative active material layer as in the case where a metallic lithium foil is laminated on the negative electrode. In this arrangement, a battery having a small internal resistance can be provided. Since the deposition of lithium is conducted in the assembled battery, lithium does not come in contact with air, preventing the formation of a thick ununiform oxidized film on the surface thereof. Thus, the deposition of dendrite can be inhibited, making it possible to inhibit the drop of battery capacity and hence provide a battery having an excellent cycle life performance. Further, lithium can be retained on the negative electrode in an amount excess to the capacity of the positive electrode. Accordingly, even when lithium is lost due to the deposition of dendrite or the reaction with the electrolyte solution, the drop of battery capacity can be inhibited because the negative electrode is provided with excess lithium.